How to use SSL_read() and SSL_accept() on non blocking
Question
I have a client/server communication that needs to be upgraded to SSL communication. Currently I have a network socket that sends and receives tcp data.
- Client issues a tcp connect() to the server.
- Server has the accept part already implemented , after accepting the connection the server enters a select loop, awaiting further op.
what I have tried:
After the tcp connect() is complete, the fd I get is what I use for openssl SSL_set_fd(ssl,fd). While on the server side after network accept I am upgrading the connection to non blocking and doing SSL_accept , calling SSL_connect() client side which is successful ( I have taken care of all the certificate and other things needed).
What I need to undertand:
SSL_accept() returns -1 with SSL_ERROR_WANT_READ, few inputs I received suggested me to put it in a 'while' loop, waiting for the ssl accept to complete. which solves it by eventually looping over many times on the ssl_accept. The confusion is if I should loop here or go back to select loop. Going back to select loop I see that the network select pops instantly back probably due to some data present due to ssl_connect. Is this the right way?
I have sent X bytes on client side with SSL_write(), which is successfully sent, when the select pops with read, I am doing an SSL_read() which does the read operation but it is less than X, so I iterate again over SSL_read() only to see 0 bytes returned in successive reads. Same question here how long should I loop aroung SSL_read() and do I have to, or got to select and wait out.
what happens if I pass SSL_read(ssl,buf,bytes) bytes more than what was received, how to handle that
I have tried SSL_pending() after first read but it always returns 0. where as there is obviously missing data. Client code
ssl = SSL_new(ctx);
SSL_set_fd(ssl, fd);
if (SSL_connect(ssl) < 0 )
{
/* Log failure */
return(-1);
} else {
ssl_write_return = SSL_write(ssl, msg , req_len);
switch(SSL_get_error(ssl, ssl_write_return))
{
case SSL_ERROR_NONE:
...
default:
...
SSL_free(ssl);
}
}
SSL_CTX_free(ctx);
Server code
ssl = SSL_new(ctx);
SSL_set_fd(ssl, session->fd);
while(TRUE){
if ((ssl_accept_ret =SSL_accept(ssl)) != 1){
log ("ssl_accept failed with %d\n", ssl_accept_ret);
switch(SSL_get_error(ssl,ssl_accept_ret )){
case SSL_ERROR_NONE:
ERR_error_string_n(ERR_get_error(), err_msg, sizeof(err_msg));
break;
case SSL_ERROR_SSL:
ERR_error_string_n(ERR_get_error(), err_msg, sizeof(err_msg));
break;
case SSL_ERROR_WANT_READ:
ERR_error_string_n(ERR_get_error(), err_msg, sizeof(err_msg));
continue;
case SSL_ERROR_WANT_WRITE:
ERR_error_string_n(ERR_get_error(), err_msg, sizeof(err_msg));
continue;
case SSL_ERROR_SYSCALL:
ERR_error_string_n(ERR_get_error(), err_msg, sizeof(err_msg));
break;
case SSL_ERROR_ZERO_RETURN:
ERR_error_string_n(ERR_get_error(), err_msg, sizeof(err_msg));
break;
case SSL_ERROR_WANT_CONNECT:
}
return(-1);
} else {
log ("ssl_accept was successful with %d\n", ssl_accept_ret);
return 0;
}
}
server read code
while(TRUE){
ret = SSL_read(session->ssl, buf, sizeof(buf));
if (ret<=0){
switch(SSL_get_error(session->ssl,ret)){
case SSL_ERROR_NONE:
ERR_error_string_n(ERR_get_error(), err_msg, sizeof(err_msg));
break;
case SSL_ERROR_ZERO_RETURN:
ERR_error_string_n(ERR_get_error(), err_msg, sizeof(err_msg));
break;
case SSL_ERROR_WANT_READ:
ERR_error_string_n(ERR_get_error(), err_msg, sizeof(err_msg));
continue;
case SSL_ERROR_WANT_WRITE:
ERR_error_string_n(ERR_get_error(), err_msg, sizeof(err_msg));
continue;
case SSL_ERROR_SYSCALL:
ERR_error_string_n(ERR_get_error(), err_msg, sizeof(err_msg));
break;
case SSL_ERROR_SSL:
ERR_error_string_n(ERR_get_error(), err_msg, sizeof(err_msg));
break;
default:
ERR_error_string_n(ERR_get_error(), err_msg, sizeof(err_msg));
break;
}
exit_select_loop()
} else {
log( "ssl_read was successful with %d and %s \n", ret,buf);
do{
ret = SSL_read(session->ssl, buf, sizeof(buf));
log("ssl_read %d and %s \n", ret,buf);
}while(SSL_pending(session->ssl)!=0 && (SSL_get_error(session->ssl, ret) == SSL_ERROR_WANT_WRITE || SSL_ERROR_WANT_READ));
}
}
1 answers
solution1
-1 2020-09-24 08:20:09
I find a working ssl code in website, you can try it:
#include <stdio.h>
#include <unistd.h>
#include <string.h>
#include <strings.h>
#include <errno.h>
#include <netinet/in.h>
#include <netdb.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <sys/time.h>
#include <sys/select.h>
#include <netinet/tcp.h>
#include <ctype.h>
#include <openssl/ssl.h>
#include <openssl/err.h>
//#include "imapfilter.h"
//#include "session.h"
#define TCP_DEFAULTBACK_LOG 15
#define HTTP_RESPON_TIMEOUT 15
//#define FORMAT_HTTPCHECK_REQ(buf,serv,port) snprintf(buf,sizeof(buf)-1,"GET /api/v1/echo/ HTTP/1.1\r\nHost: %s:%d\r\n\r\n",serv,port)
#define FORMAT_HTTPCHECK_REQ(buf,serv,port) snprintf(buf,sizeof(buf)-1,"CONNECT 192.168.1.1 HTTP/1.1\r\nHost: %s:%d\r\n\r\n",serv,port)
#if OPENSSL_VERSION_NUMBER >= 0x1010000fL
SSL_CTX *sslctx = NULL;
#else
SSL_CTX *ssl23ctx = NULL;
#ifndef OPENSSL_NO_SSL3_METHOD
SSL_CTX *ssl3ctx = NULL;
#endif
#ifndef OPENSSL_NO_TLS1_METHOD
SSL_CTX *tls1ctx = NULL;
#endif
#ifndef OPENSSL_NO_TLS1_1_METHOD
SSL_CTX *tls11ctx = NULL;
#endif
#ifndef OPENSSL_NO_TLS1_2_METHOD
SSL_CTX *tls12ctx = NULL;
#endif
#endif
/* IMAP session. */
typedef struct session {
int socket; /* Socket. */
SSL *sslconn; /* SSL connection. */
} session;
#define error printf
static int
open_connection(session *ssn,const char* serv,uint16_t port,const char* sslproto);
static int
close_connection(session *ssn);
static ssize_t
socket_read(session *ssn, char *buf, size_t len, long timeout, int timeoutfail, int *interrupt);
static ssize_t
socket_write(session *ssn, const char *buf, size_t len);
static int
open_secure_connection(session *ssn,const char* serv,const char* sslproto);
static int
close_secure_connection(session *ssn);
static ssize_t
socket_secure_read(session *ssn, char *buf, size_t len);
static ssize_t
socket_secure_write(session *ssn, const char *buf, size_t len);
/*
* Connect to mail server.
*/
static int
open_connection(session *ssn,const char* serv,uint16_t port,const char* sslproto)
{
struct addrinfo hints, *res, *ressave;
int n, sockfd;
char portstr[32];
sprintf(portstr,"%d",portstr);
memset(&hints, 0, sizeof(struct addrinfo));
hints.ai_family = AF_UNSPEC;
hints.ai_socktype = SOCK_STREAM;
n = getaddrinfo(serv, portstr, &hints, &res);
if (n < 0) {
error("gettaddrinfo; %s\n", gai_strerror(n));
return -1;
}
ressave = res;
sockfd = -1;
while (res) {
sockfd = socket(res->ai_family, res->ai_socktype,
res->ai_protocol);
if (sockfd >= 0) {
if (connect(sockfd, res->ai_addr, res->ai_addrlen) == 0)
break;
sockfd = -1;
}
res = res->ai_next;
}
if (ressave)
freeaddrinfo(ressave);
if (sockfd == -1) {
error("error while initiating connection to %s at port %d\n",
serv, port);
return -1;
}
ssn->socket = sockfd;
if (sslproto) {
if (open_secure_connection(ssn,serv,sslproto) == -1) {
close_connection(ssn);
return -1;
}
}
return ssn->socket;
}
/*
* Initialize SSL/TLS connection.
*/
static int
open_secure_connection(session *ssn,const char* serv,const char* sslproto)
{
int r, e;
SSL_CTX *ctx = NULL;
#if OPENSSL_VERSION_NUMBER >= 0x1010000fL
if (sslctx)
ctx = sslctx;
#else
if (ssl23ctx)
ctx = ssl23ctx;
if (sslproto) {
#ifndef OPENSSL_NO_SSL3_METHOD
if (ssl3ctx && !strcasecmp(sslproto, "ssl3"))
ctx = ssl3ctx;
#endif
#ifndef OPENSSL_NO_TLS1_METHOD
if (tls1ctx && !strcasecmp(sslproto, "tls1"))
ctx = tls1ctx;
#endif
#ifndef OPENSSL_NO_TLS1_1_METHOD
if (tls11ctx && !strcasecmp(sslproto, "tls1.1"))
ctx = tls11ctx;
#endif
#ifndef OPENSSL_NO_TLS1_2_METHOD
if (tls12ctx && !strcasecmp(sslproto, "tls1.2"))
ctx = tls12ctx;
#endif
}
#endif
if (ctx == NULL) {
error("initiating SSL connection to %s; protocol version "
"not supported by current build", serv);
goto fail;
}
if (!(ssn->sslconn = SSL_new(ctx)))
goto fail;
#if OPENSSL_VERSION_NUMBER >= 0x1000000fL
r = SSL_set_tlsext_host_name(ssn->sslconn, serv);
if (r == 0) {
error("failed setting the Server Name Indication (SNI) to "
"%s; %s\n", serv,
ERR_error_string(ERR_get_error(), NULL));
goto fail;
}
#endif
SSL_set_fd(ssn->sslconn, ssn->socket);
for (;;) {
if ((r = SSL_connect(ssn->sslconn)) > 0)
break;
switch (SSL_get_error(ssn->sslconn, r)) {
case SSL_ERROR_ZERO_RETURN:
error("initiating SSL connection to %s; the "
"connection has been closed cleanly\n",
serv);
goto fail;
case SSL_ERROR_NONE:
case SSL_ERROR_WANT_CONNECT:
case SSL_ERROR_WANT_ACCEPT:
case SSL_ERROR_WANT_X509_LOOKUP:
case SSL_ERROR_WANT_READ:
case SSL_ERROR_WANT_WRITE:
break;
case SSL_ERROR_SYSCALL:
e = ERR_get_error();
if (e == 0 && r == 0)
error("initiating SSL connection to %s; EOF in "
"violation of the protocol\n", serv);
else if (e == 0 && r == -1)
error("initiating SSL connection to %s; %s\n",
serv, strerror(errno));
else
error("initiating SSL connection to %s; %s\n",
serv, ERR_error_string(e, NULL));
goto fail;
case SSL_ERROR_SSL:
error("initiating SSL connection to %s; %s\n",
serv, ERR_error_string(ERR_get_error(),
NULL));
goto fail;
default:
break;
}
}
// TODO: ignore cert if (get_option_boolean("certificates") && get_cert(ssn) == -1)
// goto fail;
return 0;
fail:
ssn->sslconn = NULL;
return -1;
}
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